Electrophotographic image forming apparatuses such as photocopiers, printers, and facsimile machines have conventionally been known. Such an image forming apparatus forms an electrostatic latent image on the surface of a photoconductor, develops the electrostatic latent image by using toner, transfers the obtained toner image onto a sheet, and fixes the image. The toner for developing an electrostatic latent image is supplied from a developing apparatus to the surface of the photoconductor. To the developing apparatus, the toner is supplied from a toner cartridge, via the toner carrier apparatus. In a case where the toner cartridge is provided above the developing apparatus, the toner carrier apparatus has a toner carrying path which is vertically provided.
Since nowadays image forming apparatuses are capable of forming high-quality images, the particle size of toner has become small. Toner with small particle size typically has a low fluidity, and hence such toner tends to accumulate or coagulate in the toner carrying path of the toner carrier apparatus. A toner carrier apparatus therefore should solve such a problem.
For example, in an apparatus disclosed in Japanese Laid-Open Patent Application No. 4-174467 (published on Jun. 22, 1992), four developing devices corresponding to respective colors are provided along the vertical direction, and a toner hopper (equivalent to the toner cartridge) supplies toner to these developing devices. Each of the developing devices can move vertically, because the device is required to face a photoconductor, when the device is used. In this connection, the toner carrying path by which toner is supplied from the toner hopper to the developing devices is an accordion pipe. Also, on the side face of the accordion pipe, a rotational member is provided. This rotational member has plural protrusions in the circumferential direction, and is rotated by a motor. In other words, Japanese Laid-Open Patent Application No. 4-174467 (published on Jun. 22, 1992) teaches that the rotational member is rotated so that the outer surface of the accordion pipe is repeatedly knocked by the protrusions on the rotational member, with the result that toner remaining in the folds on the inner surface of the accordion pipe drops.
In an apparatus disclosed in Japanese Laid-Open Patent Application No. 2001-296731 (published on Oct. 26, 2001), four developing apparatuses corresponding to respective colors line up from left to right, and toner is supplied to the developing apparatus from respective toner cartridges, via first and second carrying paths. In the second toner carrying path provided in the vertical direction, a spring agitator is provided. This spring agitator vertically rocks in accordance with the rotation of an auger provided in the first carrying path which is laterally provided. In other words, Japanese Laid -Open Patent Application No. 2001-296731 (published on Oct. 26, 2001) teaches that the spring agitator vertically rocks inside the second carrying path so that adhesion of toner onto the inner wall of the second carrying path is prevented.
Japanese Laid-Open Patent Application No. 2005- 165003 (published on Jun. 23, 2005) proposes an image forming apparatus in which a communicating part between a supply pipe and a developing device is narrow. In this image forming apparatus, the narrow communicating part is widened on the occasion of toner supply, and toner is liquidized by vibrating the communicating part so that the toner is supplied to the developing device. This communicating part is made of an elastic material, in order to prevent the vibration from being transferred to the surroundings.
These conventional techniques, however, are disadvantageous in that it is not possible to properly prevent toner from accumulating or coagulating in the toner carrying path which is vertically provided.
More specifically, according to Japanese Laid-Open Patent Application No. 4-174467 (published on Jun. 22, 1992), since the vertical toner carrying path is an accordion pipe, the structure of the carrying path makes it difficult to prevent toner from accumulating or coagulating in the toner carrying path. Moreover, because a part of the toner carrying path is knocked or vibrated by the rotating member, toner tends to accumulate or coagulate at a portion away from the rotating member.
According to Japanese Laid-Open Patent Application No. 2001-296731 (published on Oct. 26, 2001), the spring agitator is provided in the vertically-provided second carrying path. On this account, toner tends to accumulate or coagulate on the surface of the spring agitator. In short, the spring agitator is liable to obstruct the carrying of toner.
According to Japanese Laid-Open Patent Application No. 2005-165003 (published on Jun. 23, 2005), the narrow communicating part vibrates at the time of supplying toner.
However, since the communicating section is made of an elastic material and hence absorbs vibration, the vibration is not sufficiently transferred from the origin of vibration. On this account, toner is likely to accumulate or coagulate at a portion away from the origin of vibration, as in the case of the document 1.